The present invention relates generally to the field of tire dynamics and more specifically to predicting the forces generated in the tire contact patch from measurements of tire deformations, including separating the lateral force and the circumferential torque using measurements of tire deformations.
U.S. Pat. No. 5,895,854, which is incorporated herein by reference, discloses a vehicle wheel that is provided with a pneumatic (rubber) tire having at least at one predetermined location a rubber mixture that is permeated with magnetizable particles that have been magnetized. As stated in that patent, the tire disclosed therein can be used in a slip regulation system. Preferably, the magnetized locations are located in one or more annular bands in the sidewall of the tire, i.e., in the longitudinal or peripheral direction, and have successive zones of different magnetization in one or more rows disposed at different radii along the peripheral direction of the tire. It was an object of that patent to provide a vehicle wheel having a pneumatic (rubber) tire, with the aid of which the information required for operating a modem vehicle, e.g. wheel rotational speed for ABS (Anti-lock Brake system) and/or longitudinal forces (torsional forces) that act upon the tire for regulating slipping, can be made available.
According to that patent, the generated magnetization and the spatial magnetization differences could be detected with magnetic field sensors and can serve as SWT sensor input signals (sidewall torsion sensor input signals) for slip regulating systems, especially also for SWT systems (sidewall torsion measuring systems). As further stated in that patent, it was previously thought that in order to be able to detect a change of the time span between the passes of the two marks (in one row for ABS or in two rows for SWT) as precisely as possible, it was desired that the magnetization in the peripheral direction be effected as quadrilaterally as possible, i.e. that the magnetization should be substantially homogeneous within a cohesive region (code bars), and above all at the boundaries of this region should change with as great a gradient as possible. In contrast, it was stated that for the conventional ABS systems that detected the wheel rotations, it was sufficient if the magnetization in the peripheral direction of the tire be effected in a sinusoidal manner.
Thus, a primary function of the SWT system using the SWT sensor has always been to measure the torsional deformation in the tangential direction of the tire and use that torsional deformation to calculate the applied driving or braking torque. However, cornering maneuvers adversely affect the calculation of driving torque or braking torque, because the presence of lateral forces on the tire confounds the measurement of longitudinal torque using the SWT sensor as originally envisioned (using phase differences between the two sensors detecting the magnetic bands in the tire sidewall to calculate torsional deformation). Additionally, the presence of a vertical force on the tire further confounds the measurement of longitudinal torque using the SWT sensor as originally envisioned, although not as severely as lateral force does.
The present invention provides a system and method for not only decoupling the lateral and tangential forces to allow the SWT sensor to be used to effectively measure longitudinal torque, but also predicting the lateral force and other forces and torques acting on the tire using the SWT sensors.
According to the present invention, a system and method are provided for predicting the forces generated in the tire contact patch from measurements of tire deformations, including separating skewed forces, e.g., lateral force and circumferential torque, using measurements of tire deformations.
According to one aspect of the system of the present invention, a trained processor, e.g., a trained neural network, is used to predict skewed forces, e.g., lateral force and circumferential torque, using measurements of tire deformations. In a first embodiment, a trained neural network is used to predict at least one force acting on the tire, preferably lateral force and circumferential torque. In a second embodiment, a set of bilinear equations are used to predict at least one force acting on the tire, preferably lateral force and circumferential torque.
It is therefore an advantage of the present invention to provide a system and method for determining circumferential torque using tire deformation sensors, e.g., SWT sensors.
It is also an advantage of the present invention to provide a system and method for determining lateral force using tire deformation sensors, e.g., SWT sensors.
It is therefore another advantage of the present invention to provide a system and method for decoupling lateral force and circumferential torque in measurements from tire deformation sensors, e.g., SWT sensors.
It is a further advantage of this invention to provide a system and method for determining vehicle yaw rate from tire deformation sensors, e.g., SWT sensors, thereby eliminating the need for a separate yaw rate sensor.
It is yet another advantage of the present invention to provide a system and method for determining vehicle speed from tire deformation sensors, e.g., SWT sensors, thereby eliminating the need for a separate speed sensor.
It is still another advantage of the present invention to provide a system and method for using a trained neural network to determine any combination or permutation of one or more of any of the following from tire deformation sensors, e.g., SWT sensors: the lateral force acting on the tire, the circumferential torque acting on the tire, the longitudinal force acting on the tire, the vertical force acting on the tire, and forces and/or torques having any one or more of the foregoing as components thereof.
It is further still another advantage of the present invention to provide a system and method for using bilinear equations to determine any combination or permutation of one or more of any of the following from tire deformation sensors, e.g., SWT sensors: the lateral force acting on the tire, the circumferential torque acting on the tire, the longitudinal force acting on the tire, the vertical force acting on the tire, and forces and/or torques having any one or more of the foregoing as components thereof.
It is another advantage of the present invention to decouple circumferential torque of a tire from lateral forces and vertical forces acting on the tire.
It is still another advantage of the present invention to provide a system and method for determining any combination or permutation of one or more of any of the following from tire sidewall deformation sensors, e.g., SWT sensors: the lateral force acting on the tire, the circumferential torque acting on the tire, the longitudinal force acting on the tire, the vertical force acting on the tire, and forces and/or torques having any one or more of the foregoing as components thereof.
These and other advantages of the present invention will become more apparent from a detailed description of the invention.